P257D code meaning
Engine Hood Switch Circuit Range/Performance
Powertrain system Generic code P25xx codes Check engine light
What P257D means
P257D is the plausibility fault of the engine hood switch. The line is electrically readable, but the value falls into a band the module regards as impossible, or two redundant switches disagree. Hood status matters because stop-start, hybrid and remote-start logic must never crank the engine while someone is working in the bay. GM's 2018 engine table 18OBDG04 rejects a resistance-coded switch reading between 1,281 and 1,404 ohms, or two discrete switches showing the same state, after 80 bad readings out of 100 taken every 12.5 ms (Type B, two trips); the 2019 hybrid table 19OBDG01 uses percentage windows instead. GM bulletin PIC6460 traces P257D on 2014–2020 Impalas to coolant creeping from the temperature sensor into the ECM connector. Hood ajar messages and blocked auto-stop are typical.
P257D at a glance
- Check engine lightYes, usually on
- Emissions testNot an emissions code
- Limp modeNot expected
- Repair difficultyMedium, DIY possible
- Typical labor0.5 to 2 hours
- Clears after repairAfter a drive cycle
Symptoms of P257D
- Check engine lamp after two drives
- Hood ajar message although the hood is closed
- Auto stop-start or remote start not available
Common causes of P257D
- Most likelyHood switch or plunger worn, misadjusted or contaminated
- PossibleFluid or corrosion in the switch or ECM connector shunting the signal
- PossibleSecond hood switch or latch switch reporting a different state
- Less likelyReplacement switch with wrong resistance coding
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Hood switch
What each part of P257D means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| 5 | Area: vehicle speed, idle control and auxiliary inputs. |
| 7D | The exact fault in that area. |
What to do next
- Note P257D and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P257D
What does P257D mean?
P257D means "Engine Hood Switch Circuit Range/Performance". P257D is the plausibility fault of the engine hood switch. It is a generic code, so it means the same on every make.
Is it safe to drive with P257D?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P257D fail an emissions test?
P257D is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is P257D to fix?
Difficulty: medium. A typical repair takes 0.5 to 2 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P257D clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.